Sir Stephen Tindall is lending his support to not-for-profit KiwiSaver scheme Simplicity.
The businessman and Simplicity founder Sam Stubbs announced $1.5 million had been invested in Simplicity via K1W1, the Tindalls' seed and venture capital fund.
Simplicity says it is one of the country's fastest-growing KiwiSaver funds, with more than 22,000 members.
The money will be used by Simplicity to pay off debt and grow the business.
Part of the would include the development of a roboadvice platform, probably delivered by phone app.
Tindall will also become patron of the Simplicity Charitable Trust, the charity governing the KiwiSaver scheme.
Tindall said his values were closely aligned with Simplicity's.
"We both want a better deal for New Zealanders. I'm delighted that we can help Simplicity grow, and that I can personally be involved."